1. Field of the Invention
The invention relates to a semiconductor device and a manufacturing method thereof.
2. Description of Related Art
The demand for a power semiconductor device having a power semiconductor element, and a power semiconductor module provided with a power semiconductor device, is increasing due to an increase in demand for power equipment having a function of a power control circuit power or a power converter circuit such as an inverter or a converter.
Insulated Gate Bipolar Transistors (IGBTs) are used as power semiconductor elements. An IGBT is a semiconductor element in which a base of a bipolar transistor has been replaced with a gate of a field-effect transistor (referred to as a “FET”). An IGBT has the high speed and the power durability of a current-drive system bipolar transistor, and the thrifty power consumption of a voltage-drive system bipolar transistor.
Japanese Patent Application Publication No. 2001-308263 (JP 2001-308263 A) describes an example in which two such IGBTs are connected in series between a high-order power supply and a low-order power supply. The two IGBTs corresponding to the high side and the low side are provided lined up from left to right. The high side IGBT is provided flipped vertically, and the low side IGBT is provided not flipped vertically. A main electrode surface on the high-order power supply side of the high side IGBT is connected to a high side plate that is a metal plate on the high side. The main electrode surface on the low-order power supply side of the high side IGBT and the main electrode surface on the high-order power supply side of the low side IGBT are connected to a middle side plate that is a metal plate midway between the high side and the low side. The main electrode surface on the low-order power supply side of the low side IGBT is connected to a low side plate that is a metal plate on the low side.
However, the semiconductor device described above has the following problems.
One of the high side IGBT and the low side IGBT is flipped vertically, and the other is not flipped vertically. As a result, when arranging the IGBTs, a process of vertically flipping one of the IGBTs must be added.
Also, when a collector electrode is formed on an electrode surface on the high-order power supply side of the IGBT, and an emitter electrode is formed on an electrode surface on the low-order power supply side of the IGBT, a spacer for heat release or height adjustment may be provided on the emitter electrode side. Also, the spacer and the emitter electrode of the high side IGBT, as well as the spacer and the middle side plate, are electrically and thermally connected by solder joints, for example. Also, the spacer and the emitter electrode of the low side IGBT, as well as the spacer and the low side plate, are electrically and thermally connected by solder joints, for example.
As described above, when one IGBT is flipped vertically, the heights of the joint locations of the IGBTs are different on the high side than they are on the low side. When inspecting the state of the joint at a joint location, such as when performing a void inspection of a solder joint location, for example, the inspection must be performed setting the focal point for each joint location height. Therefore, the inspection takes more time to perform.
Also, the foregoing problems are also common among semiconductor devices in which two IGBTs are arranged in parallel. Moreover, the foregoing problems are not limited to IGBTs, but are also common among semiconductor devices in which two of any of a variety of types of semiconductor elements including three-terminal elements or two-terminal elements are connected in series or in parallel.